1. Field of the Invention
The present invention relates to probes, and more particularly to a multipoint nanoprobe and method for manufacturing thereof.
2. Description of the Related Art
Measuring the resistance of metal films and semiconductor wafers is typically performed using multipoint probes. These probes are employed for making electrical measurements. With increased interest in the local conductivity of films, there is increased demand for smaller probe dimensions. For example, there is a great deal of interest in measuring low resistance area product (RA) tunnel junctions using Current-in-plane Tunneling, in particular, for applications such as read heads for disk drives. To be useful with current technologies, the RA needs to be roughly about 1 Ohm-micron2.
Current in-Plane Tunneling would be ideally suited for research in this highly competitive area; however, the present generation of microscopic four point probes is not well suited to measuring such a low RA stack. Specifically, data is needed at probe spacings of less than 1 micron, whereas the smallest standard microprobe in use today has a probe spacing of about 1.5 microns. There are several difficulties in making such a nanoprobe.
For example, when the individual probes of a multiprobe structure are brought closer together, they necessarily need to be narrower. This decreases the spring constant, which must be maintained at a constant value in order to ensure reproducible contact to a sample being measured. One solution may include making the probes thicker, but this cannot be continued much beyond an aspect ratio of 1:1 in thickness to width before the probes become susceptible to twisting, or etching the probes becomes difficult. Making the probes shorter to increase the spring constant is also not feasible since this decreases the amount of compliance. That is, one needs to be able to overdrive the probes a few tenths of a micron, at least, in order to make sure that all probes are in good contact. Therefore, a minimum length is perhaps roughly 5 microns, though 10 microns would be safer.
Therefore, a need exists for a multipoint probe, which maintains its elastic properties (e.g., spring constant), is relatively easy to manufacture and provides dimensional sizes, which are capable of measuring even the smallest features on a device or wafer.